Wasting your time with revenge will only disappoint you. Ignore him, grow your business and provide a better service to your clients. Good work needs no advertising.

Yep. I picked up a new client today because she was growing increasingly unhappy with the service being provided by her current (now former) lawn guy.

He comes with a zero turn and mows her small lawn, tearing up the grass when he turns on the hill, and leaves clippings all over - doesn't even do minimal trimming.

She was paying $14. I told her I couldn't do it for less than $25, that I would mow it with a push mower, and it would look a LOT better when I was finished. She was agreeable.
You see, people are often willing to pay more for better service. Those who are not, are not worth having as clients to begin with.
This woman is going to be paying nearly double what she had been paying. I didn't "steal" her away - he "pushed" her away with shoddy work, and poor communications. (never returned her calls)

If this guy is stealing your clients by offering lower prices, they aren't worth having, so don't sweat it. If he's offering, and PROVIDING better service, well you may need to look at yourself and see if you need to improve upon anything.

These guys are all giving you good advice. I have learned a lot from being on here. Much like these guys have experienced.... I had a neighborhood called Ross Bridge with 9 properties in it. Very high class but smaller yards. We offered cuts for $35/yard which was our minimum. Some kid came through and offered to cut all of our yards for $20/cut. He wasn't paying taxes like we were and he did have a business license or insurance like we did. At first I was pissed off and was going to approach the kid and possibly turn him in for running an illegal business. I quickly realized I could make much more money buy taking on bigger accounts, instead of wasting my time with $35 yards. We had a few of the yards stay with us but we decided to drop the whole route. It wasn't worth it. Instead we went out and signed a commercial property that we cut twice a month. It pays over $1,000/month. It takes us two in a half hours to cut it.

The longer you run your company the more lessons like this you will learn. All of the guys I know started out rough and learned along the way. Always do right and you will be rewarded for it. Maybe those accounts he is trying to steal from you arent worth your time to begin with. How much is your time worth? Only you can answer that. I think mine is worth a lot and so I ask a lot for it and people pay it.